1. Field of the Invention
The subject invention relates to a burn-in socket for a semiconductor package configured as a zig-zag in-line package.
2. Description of the Prior Art
Semiconductor packages are arranged with several lead configurations denoting their use. One semiconductor package is known as the zig-zag in-line package and includes a plurality of leads extending from a common side edge of the package body, every other lead being staggered to form two axial rows of package leads. Typically, all packages are tested in some manner to ensure their proper functioning, including burn-in testing where the devices are inserted into sockets and installed within large convection ovens and the packages are operated while at elevated temperatures within the ovens. The burn-in testing will accelerate the failure of those packages which would have failed early in the field, but for the burn-in testing. As it is a requirement in burn-in applications to maintain power to the package leads throughout the burn-in testing, it is a requirement specified by most package manufacturers to maintain a constant contact force on the package lead in the range of 50-100 grams when the package is inserted within the socket. Any contact force lower than 50 grams can result in discontinuity between the socket contacts and the package leads, resulting in a loss of power to the package leads. A loss of power to the package, for any time frame during the burn-in cycle, would result in a scrapped package, as the packages are rarely tested twice as the heat effect alone on the package could be detrimental to its life. Thus, if a package is not properly connected during the burn-in test, the package is discarded rather than retested.
A problem which has been experienced by one present design of burn-in socket for zig-zag in-line packages is that the terminals are folded over about their length to define two blade sections abutting partially along their length, the contact section being formed by separating the blade sections for a portion and returning the blade sections to a common contact point, the blade sections then returning to define a lead-in section. When the terminals, as described above, are inserted within the housings of the sockets, the terminals are retained at a position which is well below the portion which defines the contacting section and, therefore, the contacting section does not provide enough contact force on the package leads. Furthermore, the width of the slot which the terminal fits through, which is also the slot that retains the terminal blade portions together, is the key dimension to control the preload and the contact force between the terminal contact points and the package lead. In practice, it has been found that the width of the slot cannot be dimensionally controlled which leads to unpredictable contact force between the terminals and the package leads. This also results in the misalignment of the terminals, as the contacts can actually rock within their respective cavities resulting in permanently misaligned terminals when the sockets are soldered to the boards.
Other difficulties which have arisen relates to the fact that the packages are presently hand installed and removed from the sockets. Other types of sockets, such as sockets for dual in-line packages (DIPs), include openings beneath the package body which allows heat dissipation from the package body during the burn-in test. When the packages are finished with the burn-in cycle, a bladed tool is inserted underneath the package and pulled upwardly to remove the package end carrier. As the zig-zag in-line packages have lead portions extending down the axial centerline of the package, it is not possible to put a sword slot in the insulative housing beneath the package because pressure on the package body would damage the package leads.